And the improvements I propose also help car drivers as I've said before. Humans are remarkably capable of doing stupid things with their 1.5 tonne + vehicles that go forward with a light push from a foot on a small pedal. Roundabouts make slipping and sliding less dangerous, though still not good, variable speed limits let's traffic and weather sensors take actual information and use some math, coefficients of friction of ice (who has that in their brain at all times and the ability to use that to calculate a safe speed on an ordinary day, let alone while driving?), wind speed, anything else that would be a factor to display a speed limit that is a good speed for the conditions. Say the limit was 120 on a highway before, well now it might be 90 due to the conditions.
The air temperature is less of a factor than you might think. Of the last 3 months, at South Campus Station, it's gone below -15 not that often, maybe 10-15 days out of 90? Given good clothing, and especially face protection, that is OK to go through. And when your normal is cycling, you often just continue to do it because it's normal, and slightly less pleasant conditions will only drive few people away.
Is winter all about the snow and ice? No. We also have a lot less light to use. Visible light at least. Plenty of radio waves. It also affects us earlier than snow and ice will. It was mid November last year before we got any real snow or ice. It was about 8 AM when that happened. Some people begin to go about their journeys before then. Sunset was about 4:30 in the afternoon and many people had journeys after that time. Human eyes are tailored to see visible light, we can see UV if the lenses of our eyes were out of the equation, but then you couldn't see well anyway.
To solve these problems, the Dutch, and yes they have snow and ice, a lot of it at some times, (there was a code red ice alert in the Northeast a couple weeks ago, the conditions were so bad that everyone was advised to stay home and so something there until the alert had passed), use a variety of techniques.
The cycling paths are what their equivalent of priority 1 clearing routes are, along with roads like motorways. The paths are designed with good drainage and a sloping surface so that water drains away well, this makes ice that melts during the day has a chance to go down the drain before it can freeze. And they are wide enough so that a clearing truck, which is essentially just a pickup truck or some kind of small tractor with a brush in the front, a tank of salt water in the flat part of the truck and a sprayer for the brine in the back. That gets rid of the snow, and spreads the salt water so that ice and snow won't form again for a while. It looks wet, but it's really no big deal to ride through, especially if you have internal gears, brakes and an enclosed chain, which most people do.
The darkness can be made less of a problem with good contrasts, good lighting, in rural areas I've even found designs that incorporate small lights in the surface that guide you where the path goes, in Canada that would be a yellow light in the middle and a pair of white lights on either edge, and having good headlamps, also for people cycling, that are reliable and powered by your pedaling. Tail-lamps and reflectors on the rim of the tires and pedals help too.
Here are some examples of contrast you might not have thought of before. Look at the location depicted in the link: https://email@example.com,-113.6151409,3a,75y,359.83h,90.71t/data=!3m6!1e1!3m4!1sWRffOFrneevIZfZK1zM8Vg!2e0!7i13312!8i6656?hl=en. It made it remarkably easier to see the traffic lights and draw attention to them. The Duch do this too, just with white outlines. I've driven in BC at night where these things are standard on traffic lights. Traffic signs with better contrasts help as well.
This is an example I found from Mark Wagenbuur. I added the red box in the top right to remind people who made it.
The poles are striped, the signs have small white boxes between different coloured zones, even the paved surfaces use very different colours. It all makes a difference, because people often do crash into fixed objects in the Netherlands, not usually in pretty destructive crashes, but crashes nonetheless.
Winter is less of a factor than you think. And in fact it's actually getting better each year. Warming climate anyone?